1. Field of the Invention
The present invention relates to a scanning probe microscope utilizing a piezoelectric member as a distance control means for the probe.
2. Background Art
Conventionally there has been known, as a scanning probe microscope using a piezoelectric member as a distance controlling means for the probe, a scanning probe microscope using, for example, a tuning fork type quartz oscillator. For example, there are disclosures of scanning probe microscopes using such a tuning fork type quartz oscillator in Appl. Phys. Lett. 66(14), 1995, pp 1842-1844, by Khaled Karrai et al and in a publication of JP-A-9-89911. FIG. 10 is a schematic view of a principal part of a scanning probe microscope using a tuning fork type quartz oscillator. 400 is an optical fiber probe, and 410 is a tuning fork type quartz oscillator. The optical fiber probe is joined to a quartz oscillator by adhesion, and the quartz oscillator is oscillated by an oscillating piezoelectric member (omitted in FIG. 10). The piezoelectric oscillator if oscillated generates an electric current due to a piezoelectric effect. By detecting this current, it is possible to measure an oscillation state of the quartz oscillator. If the probe approaches a sample, the probe is acted on by a horizontal force from the sample, i.e. a shear force, and the quartz oscillator joined to the probe is changed in oscillation state. The sample-to-probe distance is adjusted using a Z-axis finely moving element (omitted in FIG. 10) in a manner of keeping constant a shear force, i.e. a change amount in amplitude or phase of a quartz oscillator output.
However, the foregoing scanning probe microscope using a conventional tuning fork type quartz oscillator has the following problems.
(1) Because the probe is adhesion-fixed to the tuning fork type quartz oscillator, the state of fixing largely varies due to environmental change such as temperature. Also, the state of the fixing portion is difficult to keep constant due to an amount of adhesive or adhesive method. As a result, vibration parameters, such as probe amplitude or Q value, varies or detection characteristics in force detection varies, resulting in instability in control.
(2) Re-utilization of the tuning fork type quartz oscillator is difficult due to fixing by adhesion.
(3) Because fixing is made such that a longitudinal direction of one surface of the tuning fork type quartz oscillator and an axial direction of the probe are parallel, the probe and the oscillator have an increased contact area. The contact area if increased makes difficult the reproducibility of the attaching state, causing an increase in the variation in vibration parameters such as probe amplitude or Q value or detection characteristic in force detection.
(4) In the tuning fork type quartz oscillator, the vibration piece not joined to the probe has an effect upon a detection signal, possibly causing malfunctioning. That is, in the case of the tuning fork type quartz oscillator, the oscillation piece joined to the probe receives a force from a sample through the probe. However, the other vibration piece maintains its natural vibrating state. In this manner, two vibration pieces are quite different in vibration state. One detects a force and changes, while the other does not change so that a resultant output does not directly reflect a force. Where this output is used as a Z servo feedback signal, there has been a defect that a probe-to-sample distance cannot be accurately controlled.
Therefore, the present invention has the following purposes.
(1) To provide a scanning probe microscope which maintains a state of a fixing portion irrespective of environmental change such as temperature or adhesive amount or adhesion method, obtaining stabilized vibration characteristics and detection characteristics.
(2) To provide a scanning probe microscope with which a detecting piezoelectric element can be reused.
(3) To provide a method of fixing a detecting piezoelectric element and probe by which a variation in vibration parameters such as probe amplitude and Q value or a variation in detection characteristic in force detection.
(4) To provide a scanning probe microscope which can accurately control a probe-to-sample distance by obtaining a detecting piezoelectric element that gives an output signal directly reflecting a force undergoing from a sample.